Water-in-oil latexes having water-soluble polymers derived from hydrophilic vinyl monomers dispersed therein are well known in the art. Such latexes have found a wide variety of uses in various areas of technology. For example, such latexes are utilized as flocculants in the mining industry and in sewage treatment applications. These latexes also have found utility in various oil field applications such as mobility control agents in enhanced oil recovery operations such as water flooding. In many of the known applications of these water-in-oil latexes of water-soluble polymers it has been desired to achieve molecular weights of the water-soluble polymers in the range of 10,000,000 and higher, even up to as high as 25,000,000. However, other applications which are being developed need water-in-oil latexes comprising water-soluble polymers having molecular weights in a lower molecular weight range e.g. less than 10,000,000.
Conventional chain transfer agents which have been proposed for use in preparing water-soluble polymers in the form of water-in-oil latexes have not always functioned effectively to provide the reduced molecular weight polymers needed in certain applications. Thus, relatively high levels of such chain transfer agents have been required to produce the requisite reduced molecular weight water-soluble polymers in the form of the water-in-oil latexes. This result not only increases the cost in producing the water-in-oil latexes of water-soluble polymers but also has the possibility of providing emulsions having very disagreeable odors resulting from residual chain transfer agents, e.g. mercaptans, when used at the rather high levels discussed above. These facts can make the water-in-oil latexes of the water-soluble polymers unsuited for many applications.
Accordingly, it is an object of my invention to provide a polymerization process for preparing water-soluble polymers in the form of water-in-oil latexes by the utilization of low levels of certain thiols in the polymerization process. Another object of my invention is to provide water-in-oil latexes of water-soluble polymers prepared by the process described above.
Other objects will become apparent from the ensuing description and the examples provided herein.